Identification and validation of a Schistosoma japonicum U6 promoter

Engineered mouse H1 promoter mutants with superior RNA polymerase III activity

Vectors incorporating the human H1 (hH1) promoter are being applied for RNA interference (RNAi) experiments and genome editing. Although extensive studies have been conducted on the hH1 promoter, our understanding of the mouse H1 promoter remains limited. In this study, we predicted the 163 bp mouse H1 (mH1) promoter and 84 bp mouse H1 core (mH1 core) promoter through global alignment and detected its RNA polymerase II (Pol II) and III activities through the expression of the EGFP and the abundance of artificial sequence, which were generally slightly weaker than those of the hH1 promoter. Furthermore, to boost its Pol III activity, we engineered various promoter mutants by introducing mutations or systematically swapping elements. Surprisingly, the Pol II activity of mH1 core mut5 with AT stretch was at least 2-fold greater than that of the wild type, making it a potential candidate for target protein expression purposes. Fortunately, the Pol III activities of mH1 mut1 and mH1 core mut5 were at least 1.5 times stronger than those of the parental promoters in human and mouse cell lines on account of AT stretch, as did the mH1 mut4 with AT stretch and proximal sequence element (PSE) and TATA box insertion mutations. We highly recommend these three promoters as valuable supplements to the type 3 Pol III promoter toolbox.

Genome editing in the edible fungus Poria cocos using CRISPR-Cas9 system integrating genome-wide off-target prediction and detection

Poria cocos is an important edible and medicinal fungus with a long history. However, the lack of adequate genetic tools has hindered molecular genetic research and the genetic modification of this species. In this study, the endogenous U6 promoters were identified by mining data from the P. cocos genome, and the promoter sequence was used to construct a sgRNA expression vector pFC332-PcU6. Then, the protoplast isolation protocol was developed, and the sgRNA-Cas9 vector was successfully transformed into the cells of P. cocos via PEG/CaCl2-mediated transformation approach. Off-target sites were genome-widely predicted and detected. As a result, the target marker gene ura3 was successfully disrupted by the CRISPR-Cas9 system. This is the first report of genome editing in P. cocos using CRISPR-Cas9 system integrating genome-wide off-target prediction and detection. These data will open up new avenues for the investigation of genetic breeding and commercial production of edible and medicinal fungus.

The tegumental allergen-like proteins of Schistosoma mansoni: A biochemical study of SmTAL4-TAL13

Schistosoma mansoni, like other trematodes, expresses a number of unusual calcium binding proteins which consist of an EF-hand domain joined to a dynein light chain-like (DLC-like) domain by a flexible linker. These proteins have been implicated in host immune responses and drug binding. Three members of this protein family from S. mansoni (SmTAL1, SmTAL2 and SmTAL3) have been well characterised biochemically. Here we characterise the remaining family members from this species (SmTAL4-13). All of these proteins form homodimers and all except SmTAL5 bind to calcium and manganese ions. SmTAL9, 10 and 11 also bind to magnesium ions. The antischistosomal drug, praziquantel interacts with SmTAL4, 5 and 8. Some family members also bind to calmodulin antagonists such as chlorpromazine and trifluoperazine. Molecular modelling suggests that all ten proteins adopt similar overall folds with the EF-hand and DLC-like domains folding discretely. Bioinformatics analyses suggest that the proteins may fall into two main categories: (i) those which bind calcium ions reversibly at the second EF-hand and may play a role in signalling (SmTAL1, 2, 8 and 12) and (ii) those which bind calcium ions at the first EF-hand and may play either signalling or structural roles (SmTAL7, 9, 10 and 13). The remaining proteins include those which do not bind calcium ions (SmTAL3 and 5) and three other proteins (SmTAL4, 6 and 11). The roles of these proteins are less clear, but they may also have structural roles.